JP7760197B2 - power supply - Google Patents

Description

The present invention relates to a power supply device, and in particular to a power supply device that stores output from a solar cell in a secondary battery cell.

In recent years, solar cells that generate electricity using solar energy have become widespread, and it has become common to use the roofs of ordinary houses and unused land for solar power generation. In such solar power generation facilities, when the amount of electricity generated by sunlight is insufficient, power is also supplied from the power grid from the power plant. Also, when the amount of electricity generated by sunlight is greater than the amount consumed, the surplus electricity can be sold through the power transmitter.

However, in remote or undeveloped areas where it is difficult to install power transmission facilities, power supply and sales using the power grid are not possible, making it difficult to install and utilize solar power generation facilities. Therefore, an independent power supply system has been proposed that combines solar cells and secondary batteries, temporarily stores the power generated by the solar cells in the secondary batteries, and then draws the power stored in the secondary batteries as needed (see, for example, Patent Document 1).

Figure 5 is a block diagram showing the configuration of a conventional independent power supply device. As shown in Figure 5, the conventional independent power supply device includes a solar cell 10, a charge/discharge control unit 20, a battery management system (BMS) 30, and a secondary battery cell 40. The output of the solar cell 10 is connected to the input of the charge/discharge control unit 20, and the output of the charge/discharge control unit 20 is connected to the battery management unit 30. The battery management unit 30 is connected to the electrode terminals of the secondary battery cell 40 and is powered by power from the secondary battery cell 40. It acquires the status of the secondary battery cell 40 and controls overcharge and overdischarge protection. The power stored in the secondary battery cell 40 is output to the load and charge/discharge control unit 20 via the battery management unit 30 and is used to drive the load and charge/discharge control unit 20.

In such a conventional independent power supply device, the charge/discharge control unit 20 and battery management unit 30 are driven by power extracted from the secondary battery cell 40, and the charge/discharge control unit 20 controls the charging and discharging operation of the secondary battery cell 40. However, when the remaining charge of the secondary battery cell 40 decreases and the over-discharge protection function of the battery management unit 30 is activated, power is no longer supplied from the secondary battery cell 40 to the charge/discharge control unit 20, causing the charge/discharge control unit 20 to stop operating and preventing the charging operation from resuming. In response to this problem, the present applicant has proposed a technology that restarts the charging and discharging operation by activating the charge/discharge control unit 20 with power supplied from the solar cell 10, even when the remaining charge of the secondary battery cell 40 decreases and over-discharge protection is activated (Patent Document 2). Furthermore, in Patent Document 2, even when the secondary battery cell 40 is in an over-discharged state, the charge/discharge control unit 20 obtains the status of the secondary battery cell 40 from the battery management unit 30 and performs a pre-charge operation to resume charging.

JP 2017-017778 A Patent No. 6031721

The prior art disclosed in Patent Document 2 uses highly interchangeable and portable secondary battery modules, allowing the secondary battery modules to be replaced as needed. This prevents further discharging in a secondary battery module that has been protected from over-discharge, leading to a deeply discharged state. Even if a secondary battery module does reach a deeply discharged state, it can be easily replaced with another secondary battery module, allowing charging and discharging operations to continue and the deeply discharged secondary battery module to be recovered.

However, with independent power supply units installed in remote locations such as those described above, it is difficult to perform repeated maintenance on the equipment in a short period of time. When there is a prolonged lack of sunlight during the rainy season or snowfall, independent power supply units in remote locations are unable to continue charging the secondary batteries. As a result, the operation of the battery management unit 30 may cause further discharge in over-discharged secondary battery cells 40, potentially leading to a deep discharge state. Because the battery management unit 30 operates on power supplied from the secondary battery cells 40, the battery management unit 30 becomes inoperative in the case of a deeply discharged secondary battery cell 40, making it impossible to resume charging. Even with the technology of Patent Document 2, the battery management unit 30 remains inoperative in the case of a deeply discharged secondary battery cell 40, making it impossible to obtain the status of the secondary battery cell 40 and therefore impossible to perform a pre-charge operation.

As described above, with conventional technology, when the remaining charge of the secondary battery cell 40 progresses to a deeply discharged state, the battery management unit 30 cannot be restarted even when sunlight returns, so the charge/discharge control unit 20 cannot perform pre-charge and charge/discharge operations, and the storage and supply of electricity generated by the solar cell 10 cannot be continued.

The present invention has been developed in consideration of the above-mentioned conventional problems, and aims to provide a power supply device that can charge the secondary battery cells and return to normal charging and discharging operation even when the remaining charge of the secondary battery cells is low and the BMS operation has stopped.

In order to solve the above problems, the power supply device of the present invention comprises a solar cell that generates electricity using light and outputs the electricity, a secondary battery cell that stores the electricity, a battery management unit that performs a protection operation by cutting off extraction of the electricity stored in the secondary battery cell when the stored voltage of the secondary battery cell is equal to or lower than a protection voltage, and an automatic return control unit that is connected between the solar cell and the battery management unit and converts a part of the electricity output by the solar cell into an automatic return current having a first voltage and a first current value, and supplies the automatic return current to the battery management unit to perform a return charging operation, The automatic recovery control unit has a first step-up/step-down unit, a step-up confirmation unit, a second step-up unit, and a constant current output unit, and the first step-up/step-down unit steps up or steps down the power input from the input terminal, adjusts it to a predetermined planned voltage, and outputs it. The step-up confirmation unit monitors the first output voltage of the first step-up/step-down unit, and operates the second step-up unit when the planned voltage is reached. The second step-up unit further steps up the planned voltage to a second output voltage and outputs it to the constant current output unit. The constant current output unit operates at the second output voltage and outputs the automatic recovery current from the output terminal to the battery management unit.

In this type of power supply device of the present invention, even if the remaining charge of the secondary battery cells is low and the battery management unit (BMS) has stopped operating, the secondary battery cells can be gradually charged using the output of the solar cells until the secondary battery cells reach or exceed their protection voltage, allowing the battery management unit to return to normal charging and discharging operation.

In one aspect of the present invention, even if the battery management unit is performing the protection operation, the automatic recovery control unit continues the recovery charging operation.

In one aspect of the present invention, a charge/discharge control unit is connected between the solar cell and the battery management unit, converts the power output from the solar cell into a charging voltage and a charging current, and supplies the converted power to the battery management unit, and the charge/discharge control unit is operated by the power stored in the secondary battery cell.

In one aspect of the present invention, the automatic recovery control unit stops the recovery charging operation when the charging voltage reaches a predetermined maximum voltage.

In one aspect of the present invention, the charge/discharge control unit uses maximum power point tracking control.

In one aspect of the present invention, the automatic recovery control unit includes a temperature measurement unit that acquires the temperature of the secondary battery cell as the cell temperature, and stops the recovery charging operation if the temperature rise of the cell temperature exceeds a predetermined protection temperature.

In one aspect of the present invention, the recovery charging operation is performed by repeating an operating state and a non-operating state of the battery management unit, and the automatic recovery current charges the secondary battery cell during the temporary operating state of the battery management unit .

The present invention provides a power supply device that can charge the secondary battery cells and return to normal charging and discharging operation even when the remaining charge of the secondary battery cells is low and the BMS operation has stopped.

1 is a block diagram schematically illustrating the configuration of a power supply device 100 according to a first embodiment. FIG. 2 is a circuit diagram showing an example of an automatic return control unit 50. 3A and 3B are timing charts showing the operation of the power supply device 100, in which FIG. 3A shows the output of the automatic return control unit 50, FIG. 3B shows the stored voltage of the secondary battery cell 40, FIG. 3C shows the operating state of the battery management unit 30, and FIG. 3D shows the charging voltage of the charge/discharge control unit 20. 3 is a flowchart showing the operation of the automatic return control unit 50 shown in FIG. 2 . FIG. 1 is a block diagram schematically illustrating the configuration of a conventionally proposed independent power supply device.

(First embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant description will be omitted where appropriate. FIG. 1 is a block diagram schematically showing the configuration of a power supply device 100 according to this embodiment. As shown in FIG. 1, the power supply device 100 of this embodiment includes a solar cell 10, a charge/discharge control unit 20, a battery management system (BMS) 30, a secondary battery cell 40, and an automatic return control unit 50.

The solar cell 10 is a photoelectric conversion device that generates electricity using light and outputs it. There are no limitations on the configuration of the solar cell 10, and it is possible to use compound semiconductor solar cells such as single crystal silicon, polycrystalline silicon, amorphous silicon, dye-sensitized silicon, and CIGS-based solar cells. The solar cell 10 may also be mounted on a stand, or installed on a road surface or wall. The output of the solar cell 10 is electrically connected to the input of the charge/discharge control unit 20, and the electricity generated by the solar cell 10 is input to the charge/discharge control unit 20.

The charge/discharge control unit 20 is electrically connected between the solar cell 10 and the battery management unit 30, converts the power output from the solar cell 10 into a charging voltage and a charging current, and supplies them to the battery management unit 30. The charge/discharge control unit 20 is composed of electronic circuits including an integrated circuit (IC), and is operated by the power stored in the secondary battery cell 40. The specific operation of the charge/discharge control unit 20 is not limited, and pulse width modulation (PWM) or maximum power point tracking (MPPT) can be used. To efficiently store the power generated by the solar cell 10 in the secondary battery cell 40, it is preferable to use the maximum power point tracking (MPPT) method.

The battery management unit 30 is electrically connected to the electrode terminals of the secondary battery cells 40 and is responsible for acquiring the status of the secondary battery cells 40 and managing over-discharge protection, over-charge protection, etc. The battery management unit 30 is composed of electronic circuits including ICs and is operated by the power stored in the secondary battery cells 40. When the stored voltage of the secondary battery cells 40 is equal to or lower than the protection voltage, the battery management unit 30 cuts off the extraction of power stored in the secondary battery cells 40 to perform over-discharge protection. Furthermore, when the stored voltage of the secondary battery cells 40 is equal to or higher than a predetermined value, the battery management unit 30 cuts off the charging operation to the secondary battery cells 40 to perform over-charge protection. The specific operation of the battery management unit 30 is not limited, and a known battery management system (BMS) can be used.

The secondary battery cell 40 stores the power supplied from the charge/discharge control unit 20 and the automatic return control unit 50 via the battery management unit 30, and also extracts the stored power via the battery management unit 30 and supplies it to the load and the charge/discharge control unit 20. The specific configuration of the secondary battery cell 40 is not limited, and lithium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, all-solid-state batteries, etc. can be used. In order to reuse resources, it is preferable to reuse lithium-ion batteries used in electric vehicles or hybrid cars as secondary battery cells 40.

The automatic return control unit 50 is connected in parallel with the charge/discharge control unit 20 between the solar cell 10 and the battery management unit 30. It converts a portion of the power output by the solar cell 10 and supplies it to the battery management unit 30. As will be described in detail below, the automatic return control unit 50 supplies current at a first voltage and a first current value to the battery management unit 30 and the secondary battery cell 40 even when the battery management unit 30 is in a stopped state (non-operating state), and performs a return charging operation on the secondary battery cell 40 until the battery management unit 30 resumes operation. The automatic return control unit 50 also continues the return charging operation even when the battery management unit 30 is performing a protective operation to cut off power extraction from the secondary battery cell 40 in an over-discharged state. The automatic return control unit 50 also stops the return charging operation when the charging voltage of the charge/discharge control unit 20 reaches a predetermined maximum voltage.

Figure 2 is a circuit diagram showing an example of the automatic return control unit 50. As shown in Figure 2, the automatic return control unit 50 includes a first step-up/step-down unit 51, a step-up confirmation unit 52, a second step-up unit 53, and a constant current output unit 54. In this embodiment, the combination of the first step-up/step-down unit 51, the step-up confirmation unit 52, and the second step-up unit 53 adjusts and outputs the power from the solar cell 10, and therefore corresponds to the voltage adjustment unit in the present invention.

The first step-up/step-down unit 51 is a circuit that boosts or lowers the power input from input terminals LP1 and LP2, adjusting it to a predetermined target voltage and outputting it. Because the output voltage of solar cell 10 fluctuates between approximately 5V and 40V, adjusting the output to a target voltage (e.g., 12V) stabilizes the operation of the constant current output unit 54, described below. In the example shown in Figure 2, the first step-up/step-down unit 51 includes a resistor R1, a Zener diode ZD1, a DC-DC converter U1, and capacitors C1 and C2. The first step-up/step-down unit 51 boosts the output of several volts from solar cell 10 to, for example, 12V and outputs it to the second step-up unit 53.

In order to reduce the impact on the automatic recovery control unit 50 when large voltage or current fluctuations occur on the solar cell 10 connected to input terminals LP1 and LP2, it is preferable to use an insulated DC-DC converter U1. By using an insulated DC-DC converter U1 and connecting input terminals LP1 and LP2 with a Zener diode ZD1, if an excessive voltage difference occurs on the solar cell 10 side, the current is short-circuited via the Zener diode ZD1, thereby reducing the adverse impact on circuits located downstream of the DC-DC converter U1.

The boost confirmation unit 52 is a circuit that monitors the output voltage of the first boost-buck unit 51 and activates the second boost unit 53 when the output voltage reaches a predetermined voltage (12 V in the example described above). In the example shown in FIG. 2, the boost confirmation unit 52 includes capacitors C3, C4, and C5, a control chip IC1, resistors R2 and R3, and a transistor Q1. In this embodiment, the boost confirmation unit 52 confirms the output voltage of the first boost-buck unit 51. Therefore, if the first boost-buck unit 51 does not sufficiently boost the voltage and does not reach the desired output, the second boost unit 53 does not perform the boost operation, and output from the constant current output unit 54 is also stopped, as described below. This allows the second boost unit 53 and the constant current output unit 54 to operate in a stable state, allowing for a stable output current to be maintained.

The second boost unit 53 is a circuit that further boosts the output from the first boost/buck unit 51 and outputs it to the constant current output unit 54. In the example shown in Figure 2, the second boost unit 53 includes capacitors C6 and C7 and a DC-DC converter U2. The DC-DC converter U2 is controlled to be driven on or off by a control signal from the boost confirmation unit 52, and boosts the input voltage by a predetermined factor before outputting it. As an example, if the output of the DC-DC converter U1 is 12V and the factor is 2, the DC-DC converter U2 will output 24V.

The constant current output unit 54 is a circuit that operates on the voltage output from the DC-DC converter U2 and outputs a constant current from output terminals LP3 and LP4 to the battery management unit 30. In the example shown in FIG. 2, the constant current output unit 54 includes a control chip IC2, resistors R4 and R5, and a variable resistor BLK1. In the example shown in FIG. 2, a backflow prevention diode SD1 is connected between the constant current output unit 54 and output terminal LP3. As an example, when the output from the DC-DC converter U2 is 24 V (first voltage), a constant current of 70 mA (first current value) is output from the constant current output unit 54.

Next, the operation of the power supply device 100 according to this embodiment will be described using Figures 3 and 4. Figure 3 is a timing chart showing the operation of the power supply device 100, where Figure 3(a) shows the output of the automatic return control unit 50, Figure 3(b) shows the stored voltage of the secondary battery cell 40, Figure 3(c) shows the operating state of the battery management unit 30, and Figure 3(d) shows the charging voltage of the charge/discharge control unit 20. Figure 4 is a flowchart showing the operation of the automatic return control unit 50 shown in Figure 2. Figures 3 and 4 assume a situation in which a lack of sunlight continues for a long period of time, causing the charge state of the secondary battery cell 40 to progress to a deeply discharged state, putting the battery management unit 30 in an inactive state, and sunlight reaching the solar cell 10.

The horizontal axis in Figures 3(a) to 3(d) represents a common time axis, with the time when sunlight reaches the solar cell 10 being set to 0. The vertical axis in Figure 3(a) represents the current value supplied from the automatic return control unit 50 to the battery management unit 30. The vertical axis in Figure 3(b) represents the stored voltage of the secondary battery cell 40, with Vmin representing the protection voltage at which the battery management unit 30 activates over-discharge protection, and Vmax representing the voltage at which the battery management unit 30 activates over-charge protection. The vertical axis in Figure 3(c) represents the operating state of the battery management unit 30, with OFF representing a non-operating state and ON representing an operating state. The vertical axis in Figure 3(d) represents the charging voltage output by the charge/discharge control unit 20 to the battery management unit 30, with max representing the maximum charging voltage set in the charge/discharge control unit 20.

In Figure 3, the period from time t=0 to t=t1 is the voltage adjustment preparation period. As shown in Figures 3(a) to 3(d), during the voltage adjustment preparation period, the output current of the automatic return control unit 50 is 0. The stored voltage of the secondary battery cell 40 is in a deep discharge state. The battery management unit 30 is in an inactive state. The charge/discharge control unit 20 is also inactive and its output is 0.

The period from time t=t1 to t=t2 is the automatic return period. As shown in Figures 3(a) to 3(d), during the automatic return period, the output current of the automatic return control unit 50 is I1. Furthermore, the stored voltage of the secondary battery cell 40 gradually rises from a deep discharge state to the over-discharge protection voltage Vmin. Furthermore, the battery management unit 30 alternates between a non-operating state and an operating state. Furthermore, the charge/discharge control unit 20 is non-operating and its output is 0.

The normal charging period is from time t=t2 to t=t3. As shown in Figures 3(a) to 3(d), during the normal charging period, the output current of the automatic recovery control unit 50 is I1. The stored voltage of the secondary battery cell 40 exceeds the over-discharge protection voltage Vmin. The battery management unit 30 is in an operating state. The charge/discharge control unit 20 is also operating, supplying the output of the solar cell 10 to the secondary battery cell 40 as a charging voltage. Here, Figures 3(b) and 3(d) show a constant rate of increase as an example of the change in the graph during the normal charging period. However, because the power generated by the solar cell 10 is supplied as a charging voltage by the charge/discharge control unit 20, the rate of increase and the fluctuations may not be constant.

The automatic recovery end period begins at time t=t3. When the charging voltage output by the charge/discharge control unit 20 reaches its maximum, the output current of the automatic recovery control unit 50 becomes 0.

As shown in Figure 4, when the automatic return operation begins, the automatic return control unit 50 adjusts the output from the solar cell 10 to a predetermined expected voltage as a preliminary adjustment operation in step S1. In the example circuit shown in Figure 2, the preliminary adjustment operation is performed by the DC-DC converter U1 of the first step-up/step-down unit 51, and continues after step S2 as long as power is being supplied from the solar cell 10.

Step S2 is a boost confirmation operation, which verifies whether the result of the preliminary adjustment operation has been adjusted to the expected voltage. In the circuit example shown in Figure 2, the boost confirmation operation is performed by control chip IC1, and a control signal is sent to DC-DC converter U2. As a specific example, boost confirmation unit 52 monitors the output from first boost/buck unit 51 and verifies whether the output of DC-DC converter U1 has been adjusted to a predetermined voltage value (expected voltage, for example 12V). If the output of DC-DC converter U1 has not reached the expected voltage, boost confirmation unit 52 sends an OFF signal and repeats the preliminary adjustment operation of step S1; if it has reached the expected voltage, it sends an ON signal and proceeds to step S3.

Step S3 is the boost output operation, which further boosts the voltage adjusted to the expected voltage in the preliminary adjustment operation and outputs a constant current at the first current value. In the circuit example shown in Figure 2, the boost output operation is performed by the DC-DC converter U2 of the second boost unit 53 and the control chip IC2. As a specific example, when the boost confirmation unit 52 sends an ON signal as a control signal to the DC-DC converter U2, the DC-DC converter U2 performs a boost operation, boosting the expected voltage (12V) to the first voltage (24V). The constant current output unit 54 is driven by the first voltage boosted by the second boost unit 53 and outputs the first current value.

In the example circuit shown in Figure 2, in steps S2 and S3, if the output of DC-DC converter U1 is not the expected voltage (12V), boost confirmation unit 52 sends an OFF signal to DC-DC converter U2. Therefore, DC-DC converter U2 does not perform boost operation, and the output is 0V and 0mA. When the output of DC-DC converter U2 reaches the expected voltage, boost confirmation unit 52 sends an ON signal to DC-DC converter U2, and DC-DC converter U2 performs boost operation and outputs a first current value (70mA) at a first voltage (24V).

During the voltage adjustment preparation period from t=0 to t=t1 in Figure 3(a), the first step-up/step-down unit 51 is unable to adjust to the planned voltage, so the second step-up unit 53 does not boost the voltage and the constant current output unit 54 does not output a current, resulting in an output current of 0. When t=t1 arrives and the step-up confirmation unit 52 confirms that the voltage has been adjusted to the planned voltage, the second step-up unit 53 boosts the voltage and the constant current output unit 54 outputs a current, and a constant current of the first current value (I1) is output from output terminals LP3 and LP4 to the battery management unit 30. This allows the constant current output from the automatic return control unit 50 to quickly change from 0 to the first current value at time t=t1, enabling a stable constant current to be output. Furthermore, the output of the solar cell 10 is not directly supplied to the battery management unit 30.

During the automatic recovery period from t=t1 to t=t2 in Figure 3, the automatic recovery control unit 50 supplies the automatic recovery current of the first voltage and first current to the battery management unit 30, and the recovery charging operation continues. When the secondary battery cell 30 is in a deeply discharged state, the battery management unit 30 is in an inactive state, but when the automatic recovery current is supplied, it temporarily enters an active state. At this time, the battery management unit 30 manages the secondary battery cell 30, but because the stored voltage is below the over-discharge protection voltage Vmin and the battery is in a deeply discharged state, it again enters an inactive state. However, even during this temporary return of the battery management unit 30 to an active state, the automatic recovery current is supplied to the secondary battery cell 40 in the charging direction, albeit for a short time, and the stored voltage rises slightly due to the recovery charging operation.

During the automatic return period, the automatic return current continues to be supplied from the automatic return control unit 50 to the battery management unit 30, causing the battery management unit 30 to repeatedly go into a state of non-operation and temporarily return to operation. During this repetition, the return charge operation repeatedly charges for short periods of time and slightly increases the stored voltage, and when the stored voltage of the secondary battery cell 40 reaches the over-discharge protection voltage Vmin at time t = t2, the battery management unit 30 allows power to be drawn from the secondary battery cell 40, allowing the operation state to continue.

After time t=t2, the stored voltage of the secondary battery cell 40 is greater than the over-discharge protection voltage Vmin, and the battery management unit 30 allows power to be drawn from the secondary battery cell 40. Therefore, the battery management unit 30 and the charge/discharge control unit 20 are operated by the output of the secondary battery cell 40, allowing the secondary battery cell 40 to continue being charged with power from the solar cell 10 and the secondary battery cell 40 to continue supplying power to the load.

Step S4 is a maximum output check operation. If the charging voltage output by the charge/discharge control unit 20 has not reached the maximum voltage max, the process proceeds to step S3; if it has reached the maximum voltage max, the process proceeds to step S5. As shown in FIG. 1, the output of the charge/discharge control unit 20 and the output of the automatic recovery control unit 50 are both connected to the battery management unit 30. Therefore, by monitoring the voltage applied to the output terminals LP3 and LP4 of the automatic recovery control unit 50, the automatic recovery control unit 50 can obtain the charging voltage output by the charge/discharge control unit 20.

Step S5 is the output stop operation, in which the automatic recovery control unit 50 stops supplying current to the battery management unit 30 at the first voltage and first current value. In the circuit example shown in Figure 2, if a voltage greater than the voltage set by the backflow prevention diode SD1 is applied to the output terminal LP3, the constant current output unit 54 stops outputting at a constant current. As a specific example, if the charging voltage of the charge/discharge control unit 20 is greater than the first voltage (24V), the automatic recovery control unit 50 performs the output stop operation.

After time t=t3, the charge/discharge control unit 20 is able to supply the charging voltage to the battery management unit 30 at the set maximum voltage, and the current value output from the automatic recovery control unit 50 becomes 0. The stored voltage of the secondary battery cell 40 is also managed by the battery management unit 30 and controlled between the over-discharge protection voltage Vmin and the over-charge protection voltage Vmax. The charge/discharge control unit 20 is powered by the power supplied from the secondary battery cell 40, and charges the secondary battery cell 30 with the power generated by the solar cell 10 via the battery management unit 30.

As described above, in the power supply device 100 of this embodiment, the automatic recovery control unit 50 is connected between the solar cell 10 and the battery management unit 30, and even when the battery management unit 30 is in a stopped state, a portion of the power output by the solar cell 10 is converted to a first voltage and a first current value and supplied to the battery management unit to perform a recovery charging operation. As a result, even when the secondary battery cell 30 is in a deeply discharged state and the battery management unit 30 is unable to extract power or acquire information from the secondary battery cell 30, the recovery charging operation can gradually charge the secondary battery cell 40. Furthermore, the power consumed by the operation of the battery management unit 30 can be reduced, allowing the recovery charging operation to continue efficiently.

In addition, the automatic return control unit 50 is connected in parallel with the charge/discharge control unit 20, so that no power is consumed by the automatic return control unit 50 when it is operating. This means that even when the output of the solar cell 10 is relatively small, the return charging operation can be continued efficiently, gradually charging the secondary battery cell 40.

Second Embodiment
Next, a second embodiment of the present invention will be described. Descriptions that overlap with the first embodiment will be omitted. In the first embodiment, the automatic recovery control unit 50 continued the recovery charge operation until the charging voltage output from the charge/discharge control unit 20 reached the maximum voltage max. In this embodiment, if the secondary battery cell 40 is short-circuited, the automatic recovery control unit 50 stops the recovery charge operation at the first voltage and first current value.

In this embodiment, the automatic return control unit 50 is equipped with a temperature measurement unit that measures the temperature of the secondary battery cell 40 and acquires cell temperature information. The automatic return control unit 50 also records the allowable temperature rise of the secondary battery cell 40 in advance as a protection temperature.

At time t=t1, when the automatic recovery control unit 50 begins to output the first current value to the battery management unit 30, the temperature measurement unit measures the temperature of the secondary battery cell 40 and acquires cell temperature information at the start of the recovery charging operation. Furthermore, while the automatic recovery control unit 50 continues the recovery charging operation and outputs the first current value to the battery management unit 30, the temperature measurement unit continues to acquire cell temperature information of the secondary battery cell 40.

The automatic recovery control unit 50 calculates the temperature rise from the start of the recovery charging operation from the acquired cell temperature information, and stops the recovery charging operation if the temperature rise exceeds the protection temperature. This is because if a fault such as a short circuit occurs inside the secondary battery cell 40, the power supplied during the recovery charging operation is not stored in the secondary battery cell 40, and instead is consumed inside the secondary battery cell 40, causing the cell temperature to rise.

As described above, in the power supply device 100 of this embodiment, the automatic recovery control unit 50 stops the recovery charging operation when the cell temperature rises above the protection temperature, thereby protecting the secondary battery cell 40 in which a failure has occurred.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

REFERENCE SIGNS LIST 100... Power supply device 10... Solar cell 20... Charge/discharge control unit 30... Battery management unit 40... Secondary battery cell 50... Automatic return control unit 51... First step-up/step-down unit 52... Step-up confirmation unit 53... Second step-up unit 54... Constant current output unit

Claims (7)

a solar cell that generates electricity using light and outputs power;
a secondary battery cell that stores the power;
a battery management unit that performs a protection operation by cutting off extraction of the power stored in the secondary battery cell when the stored voltage of the secondary battery cell is equal to or lower than a protection voltage;
an automatic recovery control unit connected between the solar cell and the battery management unit, converting a portion of the power output by the solar cell into an automatic recovery current having a first voltage and a first current value, and supplying the automatic recovery current to the battery management unit to perform a recovery charging operation;
the automatic return control unit has a first step-up/step-down unit, a step-up confirmation unit, a second step-up unit, and a constant current output unit,
the first voltage step-up/step-down unit steps up or steps down the power input from an input terminal, adjusts the power to a predetermined expected voltage, and outputs the adjusted voltage;
the boost confirmation unit monitors the first output voltage of the first boost/buck unit, and operates the second boost unit when the first output voltage reaches the expected voltage;
the second booster further boosts the scheduled voltage to a second output voltage and outputs the second output voltage to the constant current output unit;
The power supply device according to claim 1, wherein the constant current output unit operates at the second output voltage and outputs the automatic recovery current from an output terminal to the battery management unit. 2. The power supply device according to claim 1,
Even if the battery management unit is performing the protection operation,
The power supply device, wherein the automatic return control unit continues the return charging operation. 3. The power supply device according to claim 1,
a charge/discharge control unit connected between the solar cell and the battery management unit, converting the power output from the solar cell into a charging voltage and a charging current, and supplying the charging voltage and the charging current to the battery management unit;
The power supply device, wherein the charge/discharge control unit is operated by the power stored in the secondary battery cell. 4. The power supply device according to claim 3,
The power supply device, wherein the automatic recovery control unit stops the recovery charging operation when the charging voltage reaches a predetermined maximum voltage. 5. The power supply device according to claim 3,
The power supply device is characterized in that the charge/discharge control unit uses maximum power point tracking control. 6. The power supply device according to claim 1,
the automatic return control unit includes a temperature measurement unit that acquires the temperature of the secondary battery cell as a cell temperature;
A power supply device characterized in that, when the temperature rise of the cell temperature reaches or exceeds a predetermined protection temperature, the recovery charging operation is stopped. 7. The power supply device according to claim 1,
The power supply device is characterized in that the recovery charging operation is performed by the battery management unit repeatedly switching between an operating state and a non-operating state, and the automatic recovery current charges the secondary battery cell when the battery management unit is temporarily in the operating state.